Application error svchost.exe link to sound driver and internet connection

[Valpuia]

I recent have this problem which is really bugging me.
While i thought my system is running perfectly, this application error svchost.exe used to come.(not at start up)
The instruction at "0x001f1cbo" referenced memory at "0x001f1cbo". The memory could not be written. Click OK to terminate or Cancel to debug the program.
When i click OK, the sytem hang, and when i click cancel, the sounddriver which is realtek audio got corrupted right away, which i can't hear any sounds from any multimedia player (Bad sound driver)Unless the program is being opened during that time, it will continue working as long as it is not closed.If i closed the program and re run it, then there will be no sound. But the basic windows media sounds are still working. It also disturbed my wifi right away, the connection still runs but i could'nt change any access point (my hostel acess points) i could not repair the connection also. But when i restart the system everything becomes normal but after sometime the same thing happens again beginning with the application error.
I tried fixing the problem with Avast 4.8 and NOD32 and TRUE SWORD, but they do not work,(they do not detect virus, but in true sword it detect some registry error which could be fix but will come again after sometime) i believed this is the work of a virus or worms or whatever which i had no idea of the possible source.
If u guys out there know how to fix this thing, please tell me. I had tried reinstalling my OS 2 times, it comes again and again.
By the way, i'm using Windows XP professional sp2